SFT including what happens at NMJ

Question 1

What is SFT and where does it occur?

Answer 1

• Sliding Filament Theory is a mechanism involved in muscle cell contraction.
• It occurs at the molecular level

Question 2

What is the NMJ and where does it occur.

Answer 2

The Neuromuscular Junction is a synaptic connection between the terminal end of a motor nerve and a muscle. It is the site for the transmission of action potential from nerve to the muscle.

Question 3

What are the four steps of the NMJ?

Answer 3

1. Arrival of an action potential at the synaptic terminal
2. Release of acetylcholine
3. ACh binding at the motor end plate
4. Appearance of an action potential in the sarcolemma.

Question 4

What are the five stages of SFT?

Answer 4

1. Myosin heads attach to actin molecules at the binding active site.
2. Myosin “pulls” on actin (using energy from ATP), causing thin myofilaments to slide across thick myofilaments, towards the center of the sarcomere
3. As sarcomeres shorten, myofibril shortens. As myofibrils shorten, so does muscle fiber (cell)
4. Once a muscle fiber begins to contract, it will contract maximally.
5. This is known as the “all or none” principle